This invention relates to a nut adapted to eliminate the transmission of a rotary torque produced by clamping a nut to a conduit and a highly hermetically sealing fluid joint for a semiconductor fabricating apparatus provided with the same nut.
The necessity of fabricating a remarkably large scale integrated circuit has recently occurred as in a super LSI or superhigh LSI in the high acceleration of technical advancement. Since there is a requirement of using extremely toxic gaseous fluids such as a silane, an arsine or a phosphine and forming a film of high purity in a superhigh vacuum so as to fabricate such a large scale integrated circuit, this semiconductor fabricating apparatus is necessitated to maintain highly hermetical sealability.
However, in order to couple the fluid passage forming elements of such a semiconductor fabricating apparatus, it is impossible to couple by welding all the elements, and the fabricating apparatus cannot be completed unless all fluid joints have excellent hermetical sealability. There exist various types of joints used for this purpose, and there is representatively a fluid joint which, as shown in FIG. 8, couples two sleeves 1 and 2 through a gasket 3 by engaging a nut 5 clamped on the other sleeve 2 with a gland 4 formed with threads on the outer periphery on which the sleeve 1 is mounted. Since such a cap nut clamping has advantages of simplicity and no large space, the cap nuts are frequently employed in case of conduits of small diameter, but the cap nut still has drawbacks that a rotary torque is applied to the sleeve 2 due to a friction between the cap nut (female nut) 5 and the sleeve 2 and a conduit welded to the sleeve 2 is twisted due to the rotary torque and the surface of the gasket is scratched by the rotation of the sleeve 2 with the result that the fluid can leak therefrom. In order to prevent the fluid in the conduit from leaking, there is generally employed a method of clamping the cap nut while suppressing the rotation of the sleeve 2 by contacting a spanner with the chamfered position 6 of the sleeve 2 by chamfering the sleeve 2. However, since this method must suppress the rotation of the gland 4 and the sleeve 2 at the two positions and must also clamp the cap nut 5, it is impossible to operate these steps by one worker, and since the steps have to be worked very carefully, there is a drawback that the working efficiency is remarkably reduced. The inventor of this invention has invented an improved nut in which, as shown in FIG. 9, a number of small spheres 8 are held in a ring-shaped groove 9 on the surface of a cap nut 7 to be contacted under pressure with a sleeve 2 so as to eliminate the above-mentioned drawbacks.
However, since this improved nut can eliminate the above-mentioned drawbacks of the conventional nut, but the small sphere holder of the nut is required to be precisely machined to cause the nuts to have the right productivity, and there is possibility of damaging the small sphere holder if the nut is clamped by a higher torque than the specified value due to the mistake of a worker, and since the small spheres 8 are contacted at points with the sleeve 2, there arises another difficulty that the strength of the small spheres is weakened.